I too have an AT&T Lumia 920 over a year old with Windows Phone 8 (WP8).
About 7 days ago, April 10, 2014, I took some app updates and there was 2 system's area app also in the updates. I don't recall which it was...
After I downloaded all of them, I get the same issue as you - pressing the camera button or pressing the camera app tile shows the camera app for a few seconds but then it returns to home screen like it was crashing.
I have another app which uses the flash as a flashlight and this will not start now either.
Yesterday, I took the developer preview update, but this did not fix my camera problem.
Have you or any had any luck fixing the issue?
I still need a fix.
Best regards, Karhu.